Palmetto, Florida -- For 18 years, Derrick Williams sat in a prison cell professing his innocence.

In 1992, a jury convicted him for the sexual battery, kidnapping, robbery and grand theft of a woman.

Over and over, he pleaded they had the wrong guy.

Last week, his saving grace came when a judge overturned his conviction and sentence based on new DNA evidence taken from the neck ring of the suspect's t-shirt that concluded Williams had not worn it.

But, his fight wasn't quite over. The state wanted to keep him in prison while he waited for a new trial.

On Monday morning, he and his attorneys with the Innocence Project of Florida were prepping to fight to get him out of prison on bond while waiting on the new trial.

But, by Monday night, the state dropped its case and Williams was a free man.

"Can't explain it. Just filled with joy. I really don't think it's sunk in yet," he said Tuesday afternoon as he held tightly to his family.

While the state contends that Williams was correctly convicted at the 1992 trial and continues to say the evidence and testimony support his conviction, Williams and his attorneys say the t-shirt proves otherwise.

"They can't prosecute the case because Derrick Williams is innocent," said Seth Miller, executive director of the Innocence Project of Florida.

The suspect's t-shirt is one of a few pieces of evidence that remain. Miller says the rape kit and other biological evidence were destroyed by the Manatee County Sheriff's Office in 2003.

The shirt happened to be kept at the courthouse in a separate file.

"Derrick Williams is so lucky to have that shirt," said Miller.

That point isn't lost on Williams, who told 10 News, "It was by the grace of God that that was saved. Without that one piece of evidence, I wouldn't be here right now."

Even with that DNA evidence, prosecutors are still convinced the jury got it right in 1992.

Deputy Chief Assistant State Attorney, Lon Scott Arend wrote, "The state believes Derrick Williams was correctly convicted at trial in 1992 and that the evidence and testimony at the time support his conviction and sentence. In light of the recent court order, however, it has been determined that this case could not be successfully prosecuted based on the admissible evidence and it is not in the best interest of the victim to pursue a retrial."

Miller says the state's case was based on the witness testimony of the victim who pointed him out of a lineup.

"This case had the hallmarks of a wrongful conviction. It had what appeared to be a problematic or weak identification," he said.

Williams is the 10th person to be freed by the Innocence Project of Florida, which was founded in 2003.

They only learned of his plight thanks to Williams' sister-in-law Brenda Williams, who wrote them a letter pleading his case five years ago.

"I felt in my heart the whole time that he was innocent and I just knew that something could be done and God just laid it on my heart late one morning," she explained.

Five years later, she was at her brother-in-law's side celebrating his newfound freedom.

As for his first meal outside of prison? "A fish sandwich," he responded. "But, see, those are things we took, that had been missing. The small things that we go through life and take for granted. Just to be able to use your own bathroom, being able to go and make you a simple meal and I thank God for that."

Even a trip to Walmart was a whole new experience.

"You had to go through five stores to get what's in Walmart today," he laughed.

He spent most of Tuesday trying to get his documents in order so he can move on with his life outside of prison walls.

He says he's ready to work and would like to hit the road as a truck driver, like his nephew.

But, the evening was going to be spent with his son who turned 29 on Tuesday.

"It's the best birthday gift I ever gave him, getting his dad back," he said.